It is understood the problem does not involve the joint's cruciate ligament.

Chalobah left Chelsea this summer for more first-team football but now faces months out (Image: Getty)

Chalobah was expected to be named in the England squad this week and had even been earmarked to play in Lithuania on October 8, with Southgate ready to make changes if his men clinch their World Cup place against Slovenia at Wembley three days earlier.

Southgate is desperately short of midfield options, with an anchorman a particular worry, and that is why he was looking to fast-track Chalobah.

But the Hornets ace now knows he is racing the clock to regain full fitness and his best form after the operation, then prove he could do that job for England.

Southgate was expected to name the Watford man in his squad for England's final two qualifiers (Image: Getty)

Southgate is already sweating on the availability of Dele Alli, with the Tottenham midfielder potentially facing a four-game ban - ruling him out of the first two games of the World Cup - after his one-fingered gesture during last month's win over Slovakia.

Liverpool’s Jordan Henderson and Eric Dier are the regular midfielders for England, while West Brom’s Jake Livermore has established himself in the squad.

Southgate is planning to experiment away to Lithuania, especially as the game is on a plastic pitch.

Alli is also likely to be missing from the Three Lions' midfield next month after THIS (Image: Rex/Shutterstock)

He will be anxious that players do not suffer injuries and get rotated following the Slovenia game.

That could see Stoke keeper Jack Butland, Tottenham full-back Kieran Trippier and Everton defender Michael Keane all getting chances in that final qualifier.

Southgate wants to put younger players into competitive games to see how they cope and give them some much-needed experience.